Cardiovascular complications and, in particular, acute cardiovascular events are most often life threatening medical conditions which require immediate action. However, these conditions can not always be unambiguously diagnosed. Specifically, some of the most common symptoms accompanying various types of heart diseases including acute cardiovascular events, but also chronic heart dysfunctions such as chronic heart failure, are symptoms which are characteristic for other (non-cardiovascular) diseases as well. Therefore, it is often difficult, cumbersome and time consuming to differentiate between a cardiovascular or other cause of an observed symptom. Differentiation may also require the help of a specialist such as a cardiologist.
A typical symptom for cardiovascular complications, and, in particular, for an acute cardiovascular event or a more severe chronic heart failure, is shortness of breath (dyspnea). As for other symptoms, dyspnea may have various causes including cardiovascular complications and non-cardiovascular pulmonary diseases. In light of a potential cardiovascular cause of the symptom, though, it is very important to properly diagnose its cause in a given patient, e.g., an emergency patient.
As disclosed in WO2004/077056, systemic levels of surfactant proteins may be used as markers for heart failure. However, the disclosed techniques do not allow for a differential diagnosis of the cause of the elevated levels of the surfactant proteins. Specifically, it is known that pulmonary diseases or damages may also result in increased systemic levels of the proteins (Doyle 1997, Am J Respir Crit Care Med Vol. 156: 1217-1229). Accordingly, the '056 disclosed methods are highly likely to produce false positive diagnostic results, which, in turn, result in an application of inappropriate therapeutic regimen (Svendstrup Nielsen, 2004, The European Journal of Heart Failure 6: 63-70).
Therefore, there is a clear and long-standing need for means and methods permitting a differential diagnosis of the cause of symptoms such as dyspnea and, in particular, chronic dyspnea, in a subject. Desirable means and methods allow a reliable and efficient diagnosis while avoiding the drawbacks of the current techniques.
The technical problem underlying the present invention is the provision of means and methods for complying with the aforementioned needs. The technical problem is solved by the present invention as defined by the claims and as set forth below.